The present invention relates generally to centrifugal clutches and more particularly to a new and improved centrifugal clutch and flexible coupling which is fail safe and capable of transmitting motion between misaligned input and output shafts.
Centrifugal clutches coupled to turbine wheels or propeller blades are used in air-dropped ordnance to provide air velocity discrimination for weapon safety. This velocity discrimination is provided by calibrating turbine or propeller rotational velocity to the driving air velocity. In turn, the centrifugal clutch is designed to engage at a rotational velocity corresponding to the chosen threshold air velocity. The rotational motion transmitted by the engaged clutch is used for various safing-and-arming or fuzing functions to provide safety during shipment, storage, and handling of the ordnance.
Presently existing centrifugal clutches have disadvantages, particularly for ordnance applications. The clutches fail in an unsafe mode if components are omitted or malassembled. This does not satisfy the safety requirements of high explosive weapons. Additionally, if the input and output shafts are misaligned, the clutch weights generate high centrifugal, radial bearing loads at high rotational velocities, resulting in shaft bearing failures.
The disadvantages of existing centrifugal clutches are avoided in the present invention in which a novel, fail-safe, centrifugal clutch and flexible coupling provides motion transmission between an input and an output shaft for all input shaft angular velocities equal to and greater than a predetermined threshold value. The unique structure of the present invention is such that assemblies with missing or improperly assembled parts will not transmit motion at any angular velocity, and assemblies with misaligned input and output shafts will still operate even at high rotational speeds without shaft bearing failure attributable to centrifugal loading.